气井积液临界气速预测新方法

A NEW METHOD FOR PREDICTING CRITICAL GAS VELOCITIES OF LIQUID LOADING IN GAS WELLS

气井产生积液后,气体流速不足以将液体完全提升到地面,可能导致气井停产。准确预测气井临界气速可以提醒操作人员及时采取措施以预防积液发生。基于环状流最小气液界面剪切应力准则,结合管壁均匀液膜速度流场解析解,建立了临界气速预测新模型。该模型通过联立环状流的液相流量与气相动量方程得到气液界面剪切应力表达式,令其导数为零求解临界气速,简化了积液模型的求解流程。新模型考虑了井斜角、管径、压力和气芯中液滴夹带等因素对积液临界气速的影响。收集国内外不同文献中的室内实验数据以及现场生产数据,评估新模型和其他具有代表性的积液模型预测临界气速的精度,表明新模型要优于其他积液模型。对于管径为1 in、2 in、3 in、4 in、6 in垂直和倾斜管道实验室积液实验,新模型预测平均相对误差为1%;对于管径为2.441 in~4.28 in的直井和管径为1.75 in~6.18 in、井斜角为13°~64°的斜井,新模型预测的临界气速较生产数据平均相对误差不超过23%。

When a gas well suffers liquid loading,the gas velocity is not sufficient to fully lift liquid to the surface,which may kill the gas well.The accurate prediction of the critical gas velocity can remind operators to take measures in time to prevent the occurrence of liquid loading.Upon the minimum gas-liquid interface shear stress of annular flow and the velocity profile of uniform liquid film near the pipe wall,a new critical gas-velocity prediction model is proposed.By combining equations of liquid-phase flow rate and gas-phase momentum of annular flow,the expression of gas-liquid interface shear stress is obtained,and making its derivative with respect to film thickness equate to zero comes into the critical gas velocity,which simplifies the calculation.The effects of well deviation,tubing diameter,pressure,and droplet entrainment in gas core on the critical gas velocity are included in the new model.The laboratory and field data are collected to evaluate the accuracies of the new model and other typical models.The model verification shows that the new model outperforms other models.For experiments of vertical and inclined pipes with diameters of 1 in,2 in,3 in,4 in and 6 in,the average relative error of the new model is 1%.For the vertical wells with diameters of 2.441 in~4.28 in and the wells with diameters of 1.75 in~6.18 in and the deviation angles of 13°~64°,the average relative error is less than 23%.